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Learning Hadoop 2

Learning Hadoop 2

By : GABRIELE MODENA
3.8 (4)
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Learning Hadoop 2

Learning Hadoop 2

3.8 (4)
By: GABRIELE MODENA

Overview of this book

If you are a system or application developer interested in learning how to solve practical problems using the Hadoop framework, then this book is ideal for you. You are expected to be familiar with the Unix/Linux command-line interface and have some experience with the Java programming language. Familiarity with Hadoop would be a plus.
Table of Contents (13 chapters)
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12
Index

Command-line access to the HDFS filesystem


Within the Hadoop distribution, there is a command-line utility called hdfs, which is the primary way to interact with the filesystem from the command line. Run this without any arguments to see the various subcommands available. There are many, though; several are used to do things like starting or stopping various HDFS components. The general form of the hdfs command is:

hdfs <sub-command> <command> [arguments]

The two main subcommands we will use in this book are:

  • dfs: This is used for general filesystem access and manipulation, including reading/writing and accessing files and directories

  • dfsadmin: This is used for administration and maintenance of the filesystem. We will not cover this command in detail, though. Have a look at the -report command, which gives a listing of the state of the filesystem and all DataNodes:

    $ hdfs dfsadmin -report

Note

Note that the dfs and dfsadmin commands can also be used with the main Hadoop command...

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